Pitch compensating cinematographic printer



April 4, 1961 M. H. AMES PITCH COMPENSATING CINEMATOGRAPHIC PRINTER Filed March 7, 1960 R M M U t d S e Pa e .l

Malcolm H. Ames, Los Angeles, Calif., assignor to Technicolor Corporation, Hollywood, Calif., a corporation of" Maine Filed Mar. 7, 1960, Ser. No. 13,321 Claims. (Cl. 95-75) In a continuous cinematographic printer the sharpness the printed image depends on the relative pitch of the positive and negative films; if the pitches differ one film continuously slips on the other. Usually the positive is printed before processing and is stored in a sealed can, and its pitch is therefore substantially that for which it is perforated. On the other hand the negative is usual- 1y shrunken due to being in a camera for some time and because of wetting and drying in processing, the pitch being sub-standard and varying with the age of the negative. It has been proposed to compensate for the difference in pitch between negative and positive by stretching the negative emulsion and compressing the positive emulsion. However in this way it has been difficult to get accurate compensation without stretching the films around a sprocket wheel and still more difficult to adjust the compensation to different degrees of pitch difference.

Objects of the present invention are to provide a continuous printer which is simple and economical in construction, which is durable and reliable in use, and in which the aforesaid compensation may be varied throughout a wide range quickly and easily without changing sprocket wheels.

According to the present invention the printer comprises a sprocket drum, with means for pressing two films together against the drum in a line of contact, the aforesaid means comprising two presser wheels engaging the film outside their two rows of sprocket holes respectively, in combination with guides for guiding the films to and from the presser wheels so that the films bear thereon throughout an are extending on opposite sides of the aforesaid line of contact, means for transmitting light to the films in the aforesaid are along a path extending between the presser wheels, a movable support for the presser wheels so that they may be moved away from the sprocket drum, and means for detachably mounting the presser wheels on the support so that they may be readily interchanged with wheels of different diameter, the support being movable toward the sprocket drum so as to press the films against the drum irrespective of the diameter of the presser wheels, whereby the radius of the arc of contact between the films may be readily varied by interchanging the presser wheels with wheels of different diameter. In the preferred embodiment the presser wheels comprise central portions and rims detachably secured thereto so that the radii of the wheels may be varied by substituting rims of different diameters. Preferably the presser wheels are mounted on the opposed ends of stud shafts having a space therebetween to allow printing light to reach the film at the contact point. The space for the printing light path also allows room for removal of the presser wheels.

For the purpose of illustration a typical embodiment of the invention is shown in the accompanying drawings in which:

Fig. 1 is a side view; Fig. 2 is a section on line 2-2 of Fig. 1;

7 2,977,866 Patented Apr. 4, 1 961 Fig. 3 is a section on line 33 of Fig. 2; and Fig. 4 is a section on line 4-4 of Fig. l.

The particular embodiment of the invention chosen for the purpose of illustration comprises a sprocket drum 1, two presser wheels 2 bearing on the drum outside its sprocket teeth and means for. feeding negative and positive films N and P between the drum andwheels so that the films bear on the presser wheels throughout an are extending on opposite sides of the line of contact between drum and film. The presser wheels are mounted on the opposed ends of stud shafts 3 with a space between the shafts. The shafts 3 are journalled on arms 4 which are pivoted to swing about a shaft 6, the two arms being interconnected by a web 7. Also pivoted on the shaft 6 is an arm 8 carrying a lateral lug 9 which overlaps the web 7. interposed between the web 7 and the lug 9 is a compression spring 10 which yieldingly urges the presser wheels against the sprocket drum. The arm 8 is held against rotation by a lock 11 which plugs into either one of two openings 12 and 13 in the stationary frame 15. Normally the lock is plugged into the opening 12 but when the presser wheels are swung away from the sprocket drum they may be held in retracted position by plugging the lock into opening 13.

The presser wheels comprise central portions fast to the shafts 3 and rims 14 which are mounted on the central portions by means of screws 16. Mounted on one rim is a transparent internal reflecting ring 17 for printing indicia on one margin of the film by means of a light source 18.

Between the two presser wheels is a light housing 21 mounted on the frame of the machine by means of a bracket 22 and a screw 23. Mounted in the top of the housing is a lens 24 for directing the printing light from a suitable source to the two films in their are of contact.

By substituting rims 14 of different diameters the curvature of the arc of contact between the films may be varied to compensate for the difierence in pitch between the two films. To interchange rims the housing 21 is removed, the rims 14 are removed through the space between the two presser wheels and the new rims are inserted through this space, after which the light housing is returned to position. The spring 10 automatically compensates for the difference in diameter of the different presser wheels.

From the foregoing it will be evident that the negative film is stretched against the presser wheels instead of the sprocket drum. Thus the drum does not have to be changed to compensate for pitch. This is important because of the cost of making precise sprocket drums.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. A continuous cinematographic printer comprising a sprocket drum, means for pressing two films together against the sprocket drum in a line of contact, said means comprising two presser wheels engaging the films outside their two rows of sprocket holes respectively, guides for guiding the films to and from said wheels so that the films bear on the presser Wheels throughout an are extending on opposite sides of said line of contact, means for transmitting light to the films in said are along a path extending between the presser wheels, a movable support for said presser Wheels so that they may be moved away from the sprocket drum, and means for detachably mounting the presser wheels on said support so that they may be readily interchanged with wheels of different diameter, said support being movable toward the sprocket drum so as to press the films against the drum irrespective of the diameter of the presser wheels, wherebe readily varied by interchanging said presser wheels with wheels of difierent diameter.

2. A printer according to claim 1 wherein said support is pivotally mounted to swing about a radius parallel to the axis of said drum and oiiset'from the plane containing said axis and line of contact.

3. A printer according to claim 1 wherein said wheels comprise central portions and rims detachably secured thereto so that the radii of the wheels may be varied by substituting rims of different diameter.

4. A printer according to claim 1 further characterized by aligned stud shafts having a space between their opposed ends, said wheels being mounted on said ends so that they can be removed through said space.

5. A printer according to claim 4 further characterized by a light'housing in said space and means for supporting the housing so that it can'readily be removed to permit interchange of wheels. 1 V

References Cited in the file of this patent UNITED STATES PATENTS 

